Design and Kinematics for the Cystoscope of a Transurethral Continuum Surgical Robotic System

Abstract

To achieve en bloc resection of bladder tumor and the anterior tumor resection in transurethral resection of bladder tumor (TURBT), a cystoscope transurethral continuum robotic system has been proposed. A continuum cystoscope in the system needs to bend more than 180° and its base has translation, axial rotation, and tilt degrees of freedom to achieve full bladder accessibility. Under the constant-curvature assumption, the analytical solution of inverse kinematics already exists for multi-segment continuum robots with variable segment lengths and continuum robots with two inextensible segments. However, there is a lack of analytical inverse kinematics solution for continuum robots with features of the continuum cystoscope. Therefore, this paper proposes a novel and efficient inverse kinematics solving algorithm for the continuum cystoscope used in TURBT. The proposed method simplifies the inverse kinematics problem by constructing a robot plane coordinate and uses geometric relationships to derive a non-linear constraint equation containing only one intermediate variable. By solving this non-linear equation, the solution to the entire inverse kinematics problem is obtained. Additionally, based on this inverse kinematics algorithm, the length of the continuum segment is designed to ensure full bladder accessibility. In the comparative experiments with the Jacobian-based method, which involves 12500 target poses, the proposed method solves 100% of the inverse kinematics problems with a much greater computational efficiency.